Created merged_expr_t class for chained expressions

2 files changed, 102 insertions, 1 deletions

diff --git a/src/expr.cc b/src/expr.cc
index 74d16ecc..8c8e995a 100644
--- a/src/expr.cc
+++ b/src/expr.cc
@@ -163,6 +163,47 @@ void expr_t::dump(std::ostream& out) const
   if (ptr) ptr->dump(out, 0);
 }
 
+bool merged_expr_t::check_for_single_identifier(const string& expr)
+{
+  bool single_identifier = true;
+  for (const char * p = expr.c_str(); *p; ++p)
+    if (! std::isalnum(*p) || *p == '_') {
+      single_identifier = false;
+      break;
+    }
+
+  if (single_identifier) {
+    set_base_expr(expr);
+    exprs.clear();
+    return true;
+  } else {
+    return false;
+  }
+}
+
+void merged_expr_t::compile(scope_t& scope)
+{
+  if (exprs.empty()) {
+    parse(base_expr);
+  } else {
+    std::ostringstream buf;
+
+    buf << "__tmp_" << term << "=(" << term << "=(" << base_expr << ")";
+    foreach (const string& expr, exprs) {
+      if (merge_operator == ";")
+        buf << merge_operator << term << "=" << expr;
+      else
+        buf << merge_operator << "(" << expr << ")";
+    }
+    buf << ";" << term << ");__tmp_" << term;
+
+    DEBUG("expr.merged.compile", "Compiled expr: " << buf.str());
+    parse(buf.str());
+  }
+
+  expr_t::compile(scope);
+}
+
 value_t source_command(call_scope_t& args)
 {
   std::istream * in = NULL;
diff --git a/src/expr.h b/src/expr.h
index ab3487fe..5dc6430a 100644
--- a/src/expr.h
+++ b/src/expr.h
@@ -172,8 +172,68 @@ inline value_t expr_value(expr_t::ptr_op_t op) {
   return temp;
 }
 
-class call_scope_t;
+// A merged expression allows one to set an expression term, "foo", and
+// a base expression, "bar", and then merge in later expressions that
+// utilize foo.  For example:
+//
+//    foo: bar
+//  merge: foo * 10
+//  merge: foo + 20
+//
+// When this expression is finally compiled, the base and merged
+// elements are written into this:
+//
+//   __tmp=(foo=bar; foo=foo*10; foo=foo+20);__tmp
+//
+// This allows users to select flags like -O, -B or -I at any time, and
+// also combine flags such as -V and -A.
+
+class merged_expr_t : public expr_t
+{
+public:
+  string term;
+  string base_expr;
+  string merge_operator;
+  std::list<string> exprs;
+
+  merged_expr_t(const string& _term, const string& expr,
+                const string& merge_op = ";")
+    : expr_t(), term(_term), base_expr(expr), merge_operator(merge_op) {
+    TRACE_CTOR(merged_expr_t, "string, string, string");
+  }
+
+  virtual ~merged_expr_t() {
+    TRACE_DTOR(merged_expr_t);
+  }
+
+  void set_term(const string& _term) {
+    term = _term;
+  }
+  void set_base_expr(const string& expr) {
+    base_expr = expr;
+  }
+  void set_merge_operator(const string& merge_op) {
+    merge_operator = merge_op;
+  }
+
+  bool check_for_single_identifier(const string& expr);
 
+  void prepend(const string& expr) {
+    if (! check_for_single_identifier(expr))
+      exprs.push_front(expr);
+  }
+  void append(const string& expr) {
+    if (! check_for_single_identifier(expr))
+      exprs.push_back(expr);
+  }
+  void remove(const string& expr) {
+    exprs.remove(expr);
+  }
+
+  virtual void compile(scope_t& scope);
+};
+
+class call_scope_t;
 value_t source_command(call_scope_t& scope);
 
 } // namespace ledger